I don't see any need to "add LEOs back to the checkpoints". Having a LEO standing at each c/p like a bank security guard is a waste of resources; roving patrols cover much more area, require fewer LEOs, and above all, a roving patrol doesn't lull a LEO into inattentiveness from boredom, as standing a post is wont to do.

Airports are small places. Roving patrols work - as evidenced by the LAX incident - because airport terminals are small enough that no roving LEO is ever going to be more than a minute from the scene of an incident (if they are, that's a staffing and coverage issue that the local department needs to address). Yes, I know, a minute can be an awfully long time in the midst of a terrorist attack, but considering that the vast majority of the American people are content to live with police response times anywhere from 5 to 30 minutes, I think one minute or less in an airport terminal is reasonable, since active shooter scenarios are so rare in airports but other crimes like assault and theft are not.